1. Field of the Invention
The invention relates to molded plastic pulleys.
2. Description of the Prior Art
Unreinforced plastics are relatively weak and pulleys made therefrom do not have significant use. Attempts have been made to manufacture glass fiber reinforced pulleys, but these pulleys have not met with appreciable commercial success. One principal difficulty which was experienced was excessive belt wear resulting from abrasion by the glass fibers. Prior efforts to overcome this difficulty have included facing the belt engaging surfaces of the pulleys with metal coverings, as disclosed, for example, in U.S. Pat. No. 3,142,997.
Another problem was conventionally made, reinforced plastic pulleys is that the material lacks sufficient shear strength to provide strong screw threads. This made attachment of the pulleys to mounting shafts more difficult than in the case of metal pulleys. It was also difficult to connect the mating halves of adjustable V-belt pulleys to each other.